Digital printing presses in general and ink jet based printing presses in particular (e.g., printing sheets or of labels) are required to print a print job continuously and with minimum waste. Waste is defined as printed material which is not sellable, substrate which is not used to print the printed design (i.e., the product) or is printed with the design but not at acceptable quality, and thus does not generate revenue generation and the like. Ink jet nozzles have some probability of malfunctioning. The results of such a malfunction may vary. In some cases the results of such a malfunction may be substantial and noticeable in the printed image, and thus affect the usability of the material, while in other cases the result in such a malfunction may not be noticeable and thus not affect the usability of the product. A digital printing press can attempt to rectify such malfunctioning nozzles when information relating to which nozzle or nozzles (e.g., nozzle number and color) malfunctioned is available.
U.S. Pat. No. 6,637,853 to Jude Ahne et al directs to a system for detecting faulty nozzles in an ink jet printer which includes having a plurality of ink jet nozzles. The system includes a host computer and an ink jet printer and an optical sensor. The host computer generates a test pattern that is printed on a print medium. The test pattern consists of multiple test images printed in a vertical stack relative to a reference position. A start bar is printed at the reference position. Each of the test images is printed by a separate nozzle on a print head of the printer, such that there is a test image corresponding to each nozzle. For a print head having several hundred nozzles, more than one page of the print medium will be required to complete the pattern. Each page on which the pattern is printed includes a start bar at the top. If a nozzle malfunctions, there will be no test image printed corresponding to that nozzle, resulting in an empty location. The optical sensor is used to inspect the test pattern to detect any empty locations. The position of an empty location correlates to the faulty nozzle that should have printed a test image in the empty location. The host computer uses this information to modify the print data that is sent to the printer in the future.